In vitro activity: Flufenamic acids reversibly inhibits ICl(Ca) in Xenopus oocytes with IC50 of 28 mM, elicit in response to depolarizing voltage steps, in a dose-dependent manner, with no effect on the shape of the current-voltage curve. Flufenamic acids blocks Ca2(+)-activated non-selective cation channels in inside-out patches from the basolateral membrane of rat exocrine pancreatic cells with IC50 of 10 μM. Flufenamic acid binds with high affinity and negative cooperativity (pH 7.6) to wild-type (KD1=30 nM, KD2=255 nM), V30M (KD1=41 nM, KD2=320 nM) and L55P transthyretin (KD1=74 nM, KD2=682 nM), completely inhibiting amyloid fibril formation at a concentration of 10.8 μM, 3× the physiological concentration of transthyretin (3.6 μM), under conditions where transthyretin amyloid fibril formation is maximal (pH 4.4). Flufenamic acid (viz 200 μM) produces a near complete collapse of the holding current at –50 mV, mirroring the effect of removal of extracellular Ca2+. Flufenamic acid inhibits recombinant human TRPM2 (hTRPM2) as well as currents activated by intracellular ADP-ribose in the CRI-G1 rat insulinoma cell line. Flufenamic acid antagonises ADP-ribose activated currents in the rat insulinoma cell line CRI-G1 in concentration- and pH-dependent kinetics manner. Flufenamic acid reversibly inhibits (IC50 = 13.8 μM) DAPs and phasic firing with a similar time course in rat supraoptic neurones, but has no significant effects (P> 0.05) on membrane potential, spike threshold and input resistance, nor on the frequency and amplitude of spontaneous synaptic potentials.

Cell Assay: In brief, apical and basolateral chambers are filled symmetrically with Kreb's solutions. Thereafter, DMSO or Flufenamic acid is added into the basolateral chamber followed by apical membrane permealization by amphotericin B. After the amphotericin B-elicited Isc is stabilized, ouabain is added into the basolateral chamber. The ouabain sensitive Isc is used as an indicator of Na+-K+ ATPase activity.